The present invention relates to a method for fire extinguishment of burning chlorosilane compounds.
Chlorosilane compounds in general are very unstable in moisture-containing air and highly inflammable with a low flash point. Once a chlorosilane compound is set on fire, toxic gases such as hydrogen chloride are produced and the fire can hardly be extinguished by any conventional method for first extinguishment. Conventional powdery fire-extinguishing agents are quite ineffective in extinguishing fire on a burning chlorosilane compound. Moreover, the constituents of such a powdery fire-extinguishing agent sometimes react with the chlorosilane compound to accelerate evolution of toxic gases such as chlorine and hydrogen chloride.
Gaseous and liquid fire-extinguishing agents such as carbon dioxide and highly halogenated organic compounds are also not so effective for extinguishment of fire on a burning chlorosilane compound.
Naturally occurring materials such as dry sand and water are effective fire extinguishing agents for fire of most of combustion materials but they are also not quite effective for the purpose of extinguishment of fire on a burning chlorosilane compound. For example, fire on a burning chlorosilane compound cannot be extinguished with dry sand unless the volume of the sand sprinkled over the fire is very large. Certain impurities contained in sand may react with the chlorosilane eventually to produce toxic gases. Water as a fire-extinguishing agent is also not satisfactory for the purpose of extinguishing the fire on a burning chlorosilane compound because, even by setting aside the relatively low power of fire extinguishment, water reacts with all kinds of chlorosilane compounds to cause problems of evolution of toxic gases such as hydrogen chloride and fume of silica particles and formation of a large amount of gelled materials. Certain chlorosilane compounds may react with water to produce hydrogen gas which is inflammable or explosive when it is mixed with oxygen in the atmospheric air.
To give a general discussion, fire extinguishment is conducted on the base of one or a combination of any two or more of four principles including (1) removal of the combustible material from the burning site of the fire, (2) suffocation of the fire by shielding the fire from the supply source of oxygen, (3) cooling by absorbing the heat of combustion so as to decrease the temperature of the burning material below the ignition temperature thereof and (4) suppression of the fire propagation by blocking the chain-like reaction of combustion. It is of course that at least two of these principles should be combined to exhibit a synergistically more powerful effect than relying on a single principle.
In this regard, none of the conventional methods of fire extinguishment is effective for extinguishment of fire on a burning chlorosilane compound, such as trichlorosilane and methyl dichlorosilane, which is notorious in respect of the difficulty of fire extinguishment once it is set on fire, in particular, at a high temperature of 25.degree. C. or higher and a high relative humidity of 60% or more.
In U.S. Pat. No. 4,830,762, the present inventors disclosed a method for extinguishing fires on burning chlorosilane compounds utilizing an inert inorganic powder composed of silicon dioxide or a combination of silicon dioxide and aluminum oxide and thereafter, spraying water or highly halogenated liquid hydrocarbon compound over the inert powder. However, while this method is effective, it does suffer a disadvantage in that the water or highly halogenated hydrocarbon compound may be evaporated due to the heat of the burning chlorosilane compound. Thus, the beneficial effects of the water or highly halogenated hydrocarbon compound can be dissipated due to its evaporation.